Production of low-sulfur fuel oil



Nov. 10, 1970 L. R. STEENBERG ET AL 3,539,496.

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A TTORNEYS United States Patent O 3,539,496 PRODUCTION OF LOW-SULFURFUEL OIL Laurence R. Steenberg, Chicago, and Frank Stolfa, Park Ridge,111., assignors to Universal Oil Products Company, Des Plaines, Ill., acorporation of Delaware Filed Oct. 28, 1968, Ser. No. 771,244 Int. Cl.C10g 13/00, 23/00 U.S. Cl. 208-459 7 Claims ABSTRACT OF THE DISCLOSURE Aprocess for the production of low-sulfur fuel oil from sulfurous,hydrocarbonaceous black oils. The process involves the integration ofthermal cracking and fixedbed catalytic desulfurization, and isespecially applicable to those hydrocarbon charge stocks containing lessthan 150 ppm. of metallic contaminants. The charge stock is initiallycatalytically hydrogenated and desulfurized, and following separation ofthe catalytic reaction zone product effluent, a high-boiling concentrateis introduced into a thermal reaction zone, or coil. The process affordsflexibility with respect to product distribution, and particularly inregard to critical pour point and viscosity fuel oil characteristicswhere cold climate so demands.

APPLICABILITY OF INVENTION The process described herein is adaptable tothe desulfurization of petroleum crude oil residuals having a relativelylow metals content-Le. containing less than about 150 ppm. of totalmetals. More specifically, the present invention is directed toward aprocess for converting and reducing the sulfur concentration ofhydrocarbonaceous charge stocks, commonly referred to in the art asblack oils, to produce maximum quantities of fuel oil having a low pourpoint and low viscosity, as well as a sulfur concentration less thanabout 1.0% by weight.

Petroleum crude oils, and particularly the heavy residuals extractedfrom tar sands, topped or reduced crudes, vacuum residuals, etc. containhigh molecular weight sulfurous compounds in exceedingly largequantities, nitrogenous compounds, asphaltic material insoluble in lighthydrocarbons such as pentane and/or heptane, and high molecular weightorgano-metallic complexes. With respect to the latter, containing nickeland vanadium as the principal metallic components, the wide variety ofblack oil charge stocks can be classified as (1) high metals residualsor (2) low metals residuals. The present invention is primarily directedtoward the processing of those black oils having a low metals contentless than about 150 p.p.m., calculated as if existing as the element. Ablack oil is generally characterized in the petroleum refining art as aheavy carbonaceous material of which more than about 10.0% by volume hasa normal boiling point above a temperature of about 1050 F. Thishighboiling fraction is further referred to as being non-distillable.Such material generally has a gravity less than about 200 API, and iscontaminated by sulfur concentrations greater than about 2.0% by weight.Conradson carbon residue factors exceed 1.0% by weight, and a greatproportion of black oils indicate a Conradson carbon residue factorabove about 10.0.

Exemplary of those sulfurous, hydrocarbonaceous black oils, to theconversion and desulfurization of which our invention is directed,include a crude tower bottoms product having a gravity of about 143 API,and contamined by about 3.0% by weight of sulfur, 3830 ppm. of totalnitrogen, about 85 ppm. of total metals and about 11.0% by weight ofasphaltic non-distillables. Another typical charge stock is a vacuumcolumn bottoms product derived from a Mid-East crude oil. This vacuumcolumn bottoms product indicates a gravity of 60 API, an averagemolecular weight of about 620, an ASTM 20.0% by volume distillationtemperature of about 1035 F., and contains about 4,000 p.p.m. ofnitrogen, 5.5% by weight of sulfur, 100 ppm. of vanadium and nickel andabout 6.0% by weight of heptane-in'soluble asphaltenes. The presentinvention affords the conversion of such material into normally liquidhydrocarbon products of lower molecular weight, and further converts asignificant quantity of the nondistillables. Additionally, the normallyliquid product of the process has been substantially reduced in sulfurcontent, particularly in order to meet the objective of 1.0% by weightas the preferred maximum allowable in fuel oil of any character.

The principal difficulty, heretofore encountered in an attempt toprocess black oils, resides in the lack of a significant degree ofsulfur stability of catalytic composites when the charge stock ischaracterized by the presence of large quantities of asphaltic material.The difficulty arises as a consequence of the necessity for effectingthe process at operating severities such that non-distillable conversionsimultaneously takes place while the high molecular weight sulfurouscompounds are being converted into hydrogen sulfide and hydrocarbons.The asphaltic material, dispersed within the charge stock, has thetendency to fluocculate and polymerize, whereby the conversion thereofto more valuable oil-soluble products, of acceptable sulfurconcentration, is virtually precluded. Furthermore, thesulfur-containing polymerized asphaltic complexes become deposited uponthe catalytic composite employed, steadily increasing the rate at whichthe catalytic composite becomes deactivated.

The present invention is founded upon recognition of the fact thatdesulfurization of low metals-containing black oils, to a level whichmore than satisfies the current objective of a maximum 10% by weight ofsulfur, is possible at relatively mild operating severities which favorextended catalyst life. In order that the process is economicallyattractive from the standpoint of producing more valuable oil-solublehydrocarbon products, a feature of our invention resides in thesubsequent processing of the reaction product efiluent from thefixed-bed catalytic reaction zone. Therefore, as hereinafter set forthin greater detail, the catalytic reaction zone effluent is separated ata temperature which is in the range of about 650 F. to about 800 F., andpreferably at a maximum temperature of about 750 F., and atsubstantially the same pressure imposed upon the catalytic reactionzone, in order to provide a principally liquid phase, at least a portionof which is thereafter subjected to a non-catalytic, thermal crackingreaction zone, or coil.

OBJECTS AND EMBODIMENTS A principal object of our invention is toprovide an economical process for effecting the desulfurization andhydrogenative conversion of low metal black oils. A corollary objectiveis to produce maximum quantities of kerosene fractions, low pour point,low viscosity fuel oil and diesel fuel, which are significantly reducedin sulfur concentration.

Another object is to extend the period of acceptable, economicalcatalyst life while desulfurizing and converting hydrocarbonaceous blackoils containing less than about 150 ppm. of total metals.

Another object is to convert asphaltic-containing hydrocarbon chargestocks into 1ower-b0iling distillable hydrocarbons having a sulfurconcentration less than about 1.0% by weight.

Therefore, in a broad embodiment, our invention relates to a process forthe desulfurization of a sulfurous, hydrocarbonaceous black oil, whichprocess comprises the steps of: (a) heating said black oil to atemperature of from about 500 F. to about 700 F., reacting said blackoil with hydrogen in a catalytic reaction zone, in contact with acatalytic composite and at a pressure greater than about 1000 p.s.i.g.;(b) separating the resulting reaction zone effluent, in a separationzone, at substantially the same pressure imposed upon said catalyticreaction zone, to provide a first liquid phase and a first vapor phase;(c) introducing at least a portion of said first liquid phase into afractionation zone, and withdrawing a second liquid phase, having ahigher normal boiling range than said first liquid phase, from saidfractionation zone; (d) cracking at least a portion of said secondliquid phase in a non-catalytic reaction zone; (e) introducing theresulting cracked product effluent into said fractionation zone at alocus below that from which said second liquid phase is withdrawn; and(f) recovering a liquid hydrocarbon stream, reduced in sulfurconcentration, from said fractionation zone.

Other embodiments of our invention, as hereinafter set forth in greaterdetail, reside principally in the preferred ranges or process operatingvariables and in various processing techniques. For example, at least aportion of said first liquid phase is recycled to combine with saidblack oil to provide a combined liquid feed ratio to said catalyticreaction zone in the range of from about 1.05:1 to about 3.5:1.

Furthermore, the total charge to the fixed-bed catalytic reaction zone,consisting of fresh black oil charge stock, a recycled portion of thefirst liquid phase, a re cycled hydrogen-rich vapor phase and make-uphydrogen, is preferably heated to a temperature of from about 550 F. toabout 650 F. The precise temperature, to which the total charge to thereaction zone is heated, is controlled within the aforesaid range bymonitoring the temperature of the reaction zone product effluent. Sincethe principal reactions being effected are highly exothermic, atemperature rise is experienced as the charge stock and hydrogen passesthrough the catalyst bed. In some instances, a degree of temperaturecontrol is made available through the use of quench streams, introducedinto the reaction zone at intermediate points thereof. Economicallyacceptable catalyst life, particularly when the desired object entailsmaximum production of fuel oils, is achieved when the maximum catalysttemperature, which is virtually the same as that of the producteffiuent, is maintained at a maximum level below about 800 F.

In a specific embodiment, the present invention affords a process forthe conversion of a sulfurous, hydrocarbonaceous black oil, of which atleast about 10.0% boils above a temperature of about 1050 F., intolower-boiling, low viscosity fuel oil products of reduced sulfurconcentration, which process comprises the step of: (a) heating saidblack oil to a temperature of from 500 F. to about 700 F., reacting saidblack oil with hydrogen in a catalytic reaction zone, and in contactwith a catalytic composite at a pressure greater than about 1000p.s.i.g.; (b) separating the resulting reaction zone efiluent, in afirst separation zone, at substantially the same pressure imposed uponsaid first reaction zone, to provide a first vapor and a first liquidphase; (c) introducing at least a portion of said first liquid phaseinto a fractionation zone, and Withdrawing a second liquid phase, havinga higher normal boiling range than said first liquid phase, from saidfractionation zone; (d) cracking at least a portion of said secondliquid phase in a non-catalytic reaction zone, or coil; (e) introducingthe resulting cracked product effiuent into said fractionation zone at alocus below that from which said second liquid phase is withdrawn; (f)separating said first vapor phase in a second separation zone, atsubstantially the same pressure imposed upon said first separation zone,to provide a third liquid phase and a second vapor phase rich inhydrogen, and recycling said second vapor phase to combine with saidhydrocarbonaceous black oil; (g) separating said third liquid phase in athird separation zone at a pressure lower than that imposed upon saidsecond separation zone, to provide a third vaporous phase and a fourthliquid phase; (h) introducing said fourth liquid phase into saidfractionation zone at a locus above that from which said second liquidphase is withdrawn; and (i) recovering a liquid hydrocarbon stream ofreduced sulfur concentration from said fractionation zone.

A more limited embodiment involves introducing said fourth liquid phaseinto said fractionation zone at a locus above that through which saidfirst liquid phase is introduced into said fractionation zone. Otherobjects and embodiments of our invention will be evident from thefollowing, more detailed description of the process encompassed thereby.

SUMMARY OF INVENTION As hereinbefore set forth, the principal functionserved by the present invention is the production of maximum quantitiesof distillable hydrocarbons, including gasoline, kerosene, fuel oil oflow pour point and low viscosity and diesel fuel, all of which have beensubstantially reduced in sulfur concentration. Thus, our inventionaffords significant advantages in the production fuel oils for use inrelatively cold climates where pour point and viscosity are critical,and especially where the charge stock is itself highly viscous. Anotherdistinct advantage resides in the available flexibility with respect tothe product distribution of gasoline, kerosene, diesel fuel and fuel oilfractions. Of paramount importance, is the extension of the period oftime during which the fixed-bed catalytic composite functions in anacceptable manner.

With respect to the processing of high metals black oils, being thosecontaining more than about p.p.m. of total metals, it has been foundthat a successful, economical process involves initiallyhydrovisbreaking the fresh hydrocarbon charge stock in the presence oflimited quantities of hydrogen. While both technical and economicaljustification exists in support of this processing technique,particularly respecting the attainable catalyst life, there is incurreda yield loss with respect to that quantity of the originalnon-distillable asphaltics which remain unconverted. The unconvertedasphaltics are removed as a heavy residuum prior to subjecting theremainder of the thermally-cracked product effluent to additionalconversion in the fixed-bed catalytic hydrogenation/desulfurizationreaction zone. In accordance with the present process, primarilyapplicable to those charge stock of low metals content, the residualblack oil is catalytically desulfurized and hydrogenated, and at leastpartially converted at relatively mild hydrogenation severities whichfavor extended catalyst life. The catalytically converted producteffiuent is separated into a principally vaporous phase and aprincipally liquid phase, at least a portion of the latter, afterfractionation, being utilized as the charge to a noncatalytio thermalcracking reaction zone. This particular process affords maximumproduction of distillable hydrocarbons, accompanied by maximumdesulfurization of a black oil charge stock, the metals content of whichis less than about v150 p.p.m.

In a preferred embodiment, the total charge to the fixed-bed catalyticreaction zone includes the fresh hydrocarbonaceous black oil, a recycledhydrogen-rich gaseous phase, make-up hydrogen to supplant that consumedwithin the overall process and to maintain unit pressure, and a recycleddiluent, a source of the latter being hereinafter set forth. Thismixture is raised to a temperature of from about 500 F. to about 700 F.,and preferably from about 550 F. to about 650 F., as measured at theinlet to the catalyst bed. In order to preserve catalyst stability, theinlet temperature is controlled at a level such that the temperature ofthe reaction product efiiuent, or the maximum catalyst bed temperaturedoes not exceed about 800 F. The reaction zone will be maintained underan imposed pressure of from about 1000 to about 4000 p.s.i.g. andpreferably from about 1500 to about 3000 p.s.i.g. The hydrocarbon chargestock will contact the catalytic composite at a liquid hourly spacevelocity of from about 0.4 to about 10.0, based upon the fresh blackoil, exclusive of any recycled diluent. Liquid hourly space velocity(LHSV) is commonly defined as volumes of fresh liquid hydrocarbon chargestock per hour, per volume of catalyst disposed within the reactionzone. The preferred hydrogen concentration is in the range of from about5000 to about 50,000 standard cubic feet per barrel, while the combinedfeed ratio, defined as total volume of liquid charge per volume of freshblack oil charge, is in the range of from about 1.05:1 to about 3.5:1.

The catalytic composite disposed within the fixed-bed catalyticreaction, or conversion zone, can be characterized as comprising ametallic component having hydrogenation activity, which component iscombined with a suitable refractory inorganic oxide carrier material ofeither synthetic or natural origin. The precise composition and methodof manufacturing the carrier material is not considered essential to thepresent invention, although a siliceous carrier, such as 88.0% by weightof alumina and 12.0% by weight of silica, or 63.0% by weight of aluminaand 37.0% by weight of silica, or 68.0% by weight of alumina, 10.0% byweight of silica and 22.0% by weight of boron phosphate are generallypreferred. Suitable metallic components having hydrogenation activityare those selected from the group consisting of the metals of GroupsVI-B and VIII of the Periodic Table, as set forth in the Periodic Tableof the Elements, E. H. Sargent & Company, 1964. Thus, the catalyticcomposite may comprise one or more metallic components from the group ofmolybdenum, tungsten, chromium, iron, cobalt, nickel, platinum, iridium,osmium, rhodium, ruthenium, and mixtures thereof. The concentration ofthe catalytically active metallic component, or components, is primarilydependent upon a particular metal as well as the physical and/orchemical characteristics of the charge stock. For example, the metalliccomponents of Group VIB are generally present in an amount within therange of from about 1.0% to about 20.0% by weight, the irongroup metalsin an amount within the range of about 0.2% to about 10.0% by weight,whereas the noble metals of Group VIII are preferably present in anamount Within the range of from about 0.1% to about 5.0% by weight, allof which are calculated as if these components existed within thecatalytic composite in the elemental state.

Before further summarizing our invention, several definitions arebelieved necessary in order that a clear understanding be atforded. Inthe present specification and appended claims, the terms principallyvaporous and principally liquid are intended to describe a particularstream, the major proportion of the components of which is eithernormally gaseous, or normally liquid at standard conditions. Similarly,the phrase pressure substantially the same, is intended to con'note thatthe pressure under which a succeeding vessel is maintained is the sameas the previous vessel, allowing only for the pressure drop experiencedas a result of the flow of fluid through the system. Likewise, thephrase temperature substantially the same is utilized to indicate thatthe only reduction in temperature is that which stems from the normallyexperienced heat loss due to the flow of material from one piece ofequipment to another, or from the conversion of sensible heat to latentheat by flashing in which a pressure drop occurs.

The total product efiluent, from the first catalytic reaction zone, at amaximum temperature of about 800 F., and preferably at a temperature ofabout 750 F., is passed into a first separation zone hereinafterreferred to as the hot separator. The principal function served by thehot separator resides in providing recycle to the fixed-bed catalyticreaction zone. Since many black oil conversion processes require theaddition of water to the reaction zone, the hot separator further servesto remove the water in the principally vaporous phase, from which it isseparated in the cold separator. The hot separator further provides aprincipally liquid phase, the greater proportion of which boils above atemperature of about 650 F. to about 750 F. In a preferred embodiment,the total reaction product elfiuent is utilized as a heatexchange mediumin order to lower the temperature thereof to a level in the range offrom about 650 F. to about 800 F., and preferably below a level of about750 F. The principally vaporous phase from the hot separator isintroduced into a second separation zone hereinafter referred to as thecold separator. The cold separator, operating at substantially the samepressure as the hot separator, but at a significantly lower temperaturein the range of from about 60 F. to about 140 F., serves to concentratethe hydrogen in a second principally vaporous phase, and to remove waterby way of a dip-leg. This hydrogen-rich vaporous phase, comprising about83.0 mol percent hydrogen, and only about 2.1 mol percent propane andheavier hydrocarbons, is made available for utilization as a recyclestream to be combined with the fresh black oil charge stock. Butanes andheavier hydrocarbons are condensed in the cold separator, and removedtherefrom as a liquid phase which is introduced into a third separationzone.

The liquid phase from the hot separator is in part recycled to combinewith the fresh black oil charge stock, serving as a diluent for theheavier constituents thereof. The quantity of the hot separator liquidphase, diverted in this manner, is such that the combined feed ratio tothe catalytic reaction, defined as volumes of total liquid charge pervolume of fresh liquid charge, is within the range of from about 1.05:1to about 3.5: 1. The remaining portion of the liquid phase from the hotseparator is introduced into a fractionation zone at a locus in thelower portion thereof.

The fractionation zone functions at conditions of tem perature andpressure such that a bottoms fuel oil stream, having an initial boilingpoint of about 680 F., is recovered. This temperature normally definesthe initial boiling point of fuel oil as distinguished from jet fuel anddiesel fuel, and may be adjusted to either a higher, or lower level,depending upon the particular locality and current marketing demands. Itis understood that the specific initial boiling point of the fuel oilfraction is not essential to the present invention.

The condensed liquid phase separated from the cold separator isintroduced into a third separation zone, hereinafter referred to as thecold flash zone, the latter functioning at substantially the sametemperature but at a significant reduced pressure in the range of fromabout to about 400 p.s.i.g. The principal function served -by the coldflash zone is the separation of a gaseous phase principally comprisingpropane and lighter hydrocarbons, hydrogen, hydrogen sulfide andammonia, which is introduced into a light ends recovery system. A fourthliquid phase, comprising butanes, pentanes and heavier normally liquidhydrocarbons, is also separated from the cold flash zone, and introducedinto the fractionation zone at a locus above that at which the firstliquid phase from the hot separator is introduced.

That portion of the first liquid phase from the hot separator, not beingdiverted as recycled diluent to combine with the black oil charge stock,is introduced into the fractionation zone at a locus above that fromwhich the 680 F.-plus fuel oil fraction is removed. A second liquidphase, having a normal boiling range higher than that of the firstliquid phase, is introduced into a thermal cracking reaction zone, orcoil, at a pressure of from about 200 to about 400 p.s.i.g. and atemperature of from about 700 to about 750 F. The thermally-crackedproduct efliuent, at a temperature of from about 900 F. to about 950 F.,is introduced into the fractionation zone at a locus in the lowerportion thereof, and below that 7 from which the second liquid phase,serving as the charge to the thermal reaction coil, is withdrawn.Temperature control of the reboiler section of the fraction zone isfacilitated by withdrawing a heart-cut from an intermediate locus, andcombining the same with the thermally-cracked product effluent.

The principal advantage, or benefit, attendant the utilization of ourinvention, resides in the production of maximum quantities of lowviscosity, low pour point fuel oil, diesel fuel, and gasoline andkerosene fractions, all of which are significantly reduced in sulfurconcentration. Another, closely related advantage is that the processaffords a great degree of flexibility with respect to the quantities ofthe various fuel oil streams. For example, the operating conditions ofthe fixed-bed catalytic reaction zone can be adjusted to vary thequantities of jet fuel, diesel fuel and fuel oil to some extent,providing care is exercised to insure that the fuel oil meets thespecification of a maximum of 1.0% by weight of sulfur. Similarly, thefractionation zone temperature and pressure can be adjusted to vary theboiling range of the second liquid phase utilized as the charge to thethermal reaction zone, or coil.

Another important advantage, or benefit, resides in an extension of theperiod of acceptable catalyst life with respect to the fixed-bedcatalytic reaction zone. This stems primarily from the fact thatdesulfurization, to a level less than about 1.0% by weight, is effectedat a relatively low severity of operation with the result that theatmosphere within the catalytic reaction zone is not conducive to theformation of sulfur-containing polymer products, otherwise resultingfrom the presence of hydrocarbon-insoluble asphaltenes. Of furtherinterest is the fact that no vacuum flash column is necessary in orderto concentrate the fuel oil boiling above a temperature of about 680 F.This as will be recognized by those having skill in the art of petroleumprocessing techniques, affords a significant advantage with respect tothe overall economics of the process.

DESCRIPTION OF DRAWING For the purpose of demonstrating the illustratedembodiment, the drawing will be described in connection with theconversion of a vacuum column bottoms, derived from a Middle-East crudeoil blend, into maximum quantities of fuel oil. This particular vacuumcolumn bottoms product indicates a gravity of about 165 API, an averagemolecular weight of about 510, an ASTM 50.0% volumetric distillationtemperature of about 930 F., and contains about 3.60% by weight ofsulfur, 2190 p.p.m. of nitrogen, 54 ppm. of vanadium and nickel, has aConradson carbon residue factor of about 9.0% by weight and containsabout 3.0% by weight of heptane-insoluble asphaltenes.

In addition, the description will be directed toward acommercially-scaled unit having a design capacity of about 40,000barrels per day. In the drawing, the embodiment is presented by means ofa simplified flow diagram in which details such as pumps,instrumentation and controls, heat-exchange and heat-recovery circuits,valving, start-up lines and similar hardware have been omitted asnon-essential to an understanding of the invention and the techniquesinvolved. The utilization of such miscellaneous appurtenances, to modifythe illustrated process flow, are well within the purview of thoseskilled in the art. Similarly, it is understood that the charge stock,stream compositions, and boiling ranges, operating conditions, design offractionators, separators and the like, are illustrative only and may bevaried widely without departure from the spirit of our invention, thescope of which is defined by the appended claims.

This particular vacuumcolumn bottoms charge is intended for conversioninto high yields of low viscosity, low pour point fuel oil which has aninitial boiling point of from 450 F. to 680 F., while maximizing thevolumetric yields of kerosene and gasoline boiling range fractions. Thecharge stock is processed in a fixed-bed catalytic conversion zone inadmixture with about 10,000 standard cubic feet per barrel of hydrogen,based upon fresh black oil charge stock, at an inlet catalysttemperature of about 650 F. and an inlet pressure of about 2000 p.s.i.g.The liquid hoursly space velocity, based upon fresh feed only, is 0.74,and the combined feed ratio, with respect to total liquid feed, is about1.5:1. With reference now to the drawing, the vacuum column bottoms inan amount of about 41,000 barrels per day, is introduced into theprocess by way of line 1, is admixed with about 20,500 barrels per dayof a hot separator liquid stream in line 2 and a recycled hydrogen-richgaseous phase, in an amount of about 10,000 standard cubic feet perbarrel, in line 3, the mixture continuing through line 1 into heater 5.Not illustrated in the drawing is the technique whereby the total chargeto heater 5 is initially heated by way of conventional heatexchangefacilities with various hot eflluent streams to a temperature of about575 F. Heater 5 raises the temperature of the feed mixture to a level of650 F., the heated mixture passing through line 6 into fixed-bedcatalytic reactor 7.

The product effiuent, in mixed-phase in line 8, at a temperature ofabout 750 F., is utilized as a heatexchange medium in order to lower thetemperature to about 700 R, and enters hot separator 9 at a pressure ofabout 1950 p.s.i.g. A principally vaporous phase is withdrawn from a hotseparator 9 by way of line 10 and, after cooling by conventional means,is introduced into cold separator 11 at a temperature of about 100 F.and a pressure of about 1900 p.s.i.g. A hydrogen-rich gaseous phase isremoved from cold separator 11 by way of line 3 through the use ofcompressive means not illustrated in the drawing. After make-up hydrogenis introduced via line 4, the gaseous mixture continues through line 3to be combined with the liquid feed mixture in line 1. A liquid phasefrom cold separator 11, comprising principally butanes and heaviernormally liquid hydrocarbons, is withdrawn from cold separator 11 by wayof line 14, and is introduced into cold flash zone 15.

A principally liquid phase, containing some dissolved hydrogen and lightnormally gaseous hydrocarbons, is withdrawn from hot separator 9 throughline 12, a portion thereof being diverted by way of line 2 as recycleddiluent for the fresh charge stock in line 1. The remaining portion ofthe hot separator liquid stream continues through line 12, beingintroduced thereby into fractionation zone 13.

Cold flash zone 15 serves to concentrate further butanes and heavierhydrocarbons, as a fourth liquid phase in line 17. Methane, ethane andpropane, and hydrogen, hydrogen sulfide, and ammonia are removed fromcold flash 15 to a light ends recovery system by way of line 16. Thefourth liquid phase in line 17 is introduced into fractionation zone 13at a locus above that through which the first liquid phase in line 12 isintroduced.

A second liquid phase, comprising primarily normally liquid hydrocarbonshaving a boiling range above about 600 F., is withdrawn fromfractionation zone 13 by way of line 23, and introduced therethroughinto thermal coil 24 at a temperature of about 700 F., and a pressure ofabout 400 p.s.i.g. The thermally-cracked product efliuent, at a pressureof about 50 p.s.i.g., and a temperature of about 930 F., and inadmixture with a side-cut in line 22, is introduced into fractionationzone 13 by way of line 25' and at a locus below that from which thesecond liquid phase is withdrawn by way of line 23.

As hereinbefore set forth, fractionation zone 13 functions at conditionsof temperature and pressure such that an overhead stream consistingprimarily of butanes and lighter hydrocarbons is removed via line 18,and a fuel oil fraction comprising hydrocarbonaceous material boilingabove a temperature of about 680 -F., is removed as a bottoms product byway of line 21. A gasoline boiling range fraction, in the illustrationcontaining pentanes and hydrocarbons boiling up to a temperature ofabout 330 F, is withdrawn as an intermediate side-cut by way of line 19.In the illustration, the jet fuel fraction, boiling from about 330 F. toabout 450 F., and the diesel fuel fraction boiling from about 450 F. toabout 680 F., are indicated as being withdrawn as a single side-cut byway of line 20.

In order to further illustrate the process of the present invention, thefollowing Table I indicates the composition of the reaction producteflluent from fixed-bed catalytic reaction zone 7, exclusive of anyrecycle and/or quench streams.

TABLE I.-CATALYTIC REACTION ZONE YIELDS Component Wt. percent Vol.percent Ammonia 0.

680 FI-plus TABLE II.PRODUCT YIELD AND DISTRIBUTION BbL/day ComponentWt. percent Vol. percent Ammonia 0. 10

0. 73 1. 21 495 Pentanes l 0. 92 1. 40 575 Hexanes-330 F 4. 61 5. 97 2,450 330 F.450 F-.- 5. 84 6. 99 2, 860 450 F.680 F 16. 70 18. 93 7, 750680 FrPlllS 67. 72 68. 77 28, 270

The naphtha, or gasoline boiling range fraction, hexanes to 330 'F., hasa gravity of 602 API and contains 0.1% by Weight of sulfur. The kerosenecut, 330 F. to 450 'F., contains only 0.15% by Weight of sulfur, andindicates a gravity of 363 API. Of further interest is the fact that thediesel fuel fraction, 450 F. to 680 F., has a gravity of 363 API andcontains 0.5% by Weight of sulfur, while the fuel oil fraction, 680 F.-plus, has a gravity of 18.8 API and contains about 0.95% by Weight ofsulfur. In order to meet the pour point and viscosity requirementdictated by relatively cold climates, the diesel fuel and fuel oilfractions are blended. The quantities of each fraction, which go to makeup the :final blend, will vary from one locale to another, as well asfrom one season to another in any given locale. For illustrativepurposes, it will be assumed desirable to blend both fractions en toto.In this manner, 36,020 bbl./day are produced by the present process, andthe pour point is about F.- F, with the viscosity being about 100 cst.In the situation involving only the fixed-bed catalytic reaction zone,the viscosity would be 200 cst. and the pour point in the range of F. F.

The foregoing specification, and particularly the example integratedinto the description of the drawing, indicates the benefits affordedthrough the utilization of our invention. From a fresh black oil chargeof about 41,000 barrels per day, there is produced 42,400 barrels perday of distillable hydrocarbon products, including butanes which havevalue, for example, as motor fuel blending components. Of furtherinterest is the fact that the chemical consumption of hydrogen, in theoverall process, is only about 0.83% by weight of the total black oilcharge stock.

We claim as our invention:

1. A process for the desulfurization of a sulfurous, hydrocarbonaceousblack oil which comprises the steps of.

(a) heating said black oil to a temperature of from 500 F. to about 700F., reacting said black oil with hydrogen in a catalytic reaction zone,in contact with a catalytic composite and at a pressure greater thanabout 1000 p.s.i.g.;

(b) separating the resulting reaction zone effluent, in a separationzone, at substantially the same pressure imposed upon said catalyticreaction zone, to provide a first liquid phase and a first vapor phase;

(c) introducing at least a portion of said first liquid phase into afractionation zone, and withdrawing a second liquid phase, having ahigher normal boiling range than said first liquid phase from saidfractionation zone;

(d) cracking at least a portion of said second liquid phase in anon-catalytic reaction zone;

(e) introducing the resulting cracked product efiiuent into saidfractionation zone at a locus below that from which said second liquidphase is withdrawn; and

(f) recovering a normally liquid hydrocarbon stream,

reduced in sulfur concentration, from said fractionation zone.

2. The process of claim 1 further characterized in that at least aportion of said first liquid phase is recycled to combine with saidblack oil to provide a combined liquid feed ratio to said catalyticreaction zone in the range of from 1.05:1 to about 35:1.

3. The process of claim 1 further characterized in that said catalyticreaction zone efliuent is introduced into said separation zone at atemperature of from about 700 F. to about 800 F.

4. The process of claim 1 further characterized in that said first vaporphase is separated in a second separation zone at substantially the samepressure imposed upon said first separation zone, to provide a thirdliquid phase and a second vapor phase rich in hydrogen, and recyclingsaid second vapor phase to combine with said charge stock.

5. A process for the conversion of a sulfurous, hydrocarbonaceous blackoil, of which at least about 10.0% boils above a temperature of about1050 F., into lowerboiling hydrocarbon products of reduced sulfurconcentration, which process comprises the steps of:

(a) heating said black oil to a temperature of from about 500 F. toabout 700 F., reacting said black oil With hydrogen in a catalyticreaction zone, and in contact with a catalytic composite at a pressuregreater than about 1000 p.s.i.g.;

(b) separating the resulting reaction zone efiluent, in a firstseparation zone, at substantially the same pressure imposed upon saidfirst reaction zone, to provide a first vapor phase and a first liquidphase;

(0) introducing at least a portion of said first liquid phase into afractionation zone, and withdrawing a second liquid phase, having ahigher normal boiling range than said first liquid phase, from saidfractionation zone;

(d) cracking at least a portion of said second liquid phase in anon-catalytic reaction zone;

(e) introducing the resulting cracked product efiiuent into saidfractionation zone at a locus below that from which said second liquidphase is withdrawn;

(f) separating said first vapor phase in a second separation zone, atsubstantially the same pressure imposed upon said first separation zone,to provide a third liquid phase and a second vapor phase rich inhydrogen, and recycling said second vapor phase to combine with saidhydrocarbonaceous black oil;

(g) separating said third liquid phase in a third separation zone at apressure lower than that imposed upon said second separation zone, toprovide a third vaporous phase and a fourth liquid phase;

(h) introducing said fourth liquid phase into said fractionation zone ata locus above that from which said second liquid phase is withdrawn; and

(a) recovering a liquid hydrocarbon stream of re duced sulfurconcentration from said fractionation zone.

6. The process of claim 5 further characterized in that said black oilis heated to a temperature of from about 550 F. to about 650 F.

7. The process of claim 5 further characterized in that said fourthliquid phase is introduced into said fraction zone at a locus above thatthrough which said first liquid phase is introduced into saidfractionation zone.

References Cited UNITED STATES PATENTS 10/1933 Gaus et al. 19624 5/1942Brooks 196-24 8/1943 Eastman 196-49 1/1944 Thomas 19652 8/ 1944 Conn196-24 11/1968 Gleim 20859 US. Cl. X.R.

